Develop Reference

Create Windows Symbolic Link with Java (equivalent to MKLINK)

Could anyone please tell me how to make a symbolic link (in the same way MKLINK does) and/or remove a symbolic link with Java. I have found solutions that use Java as a wrapper and use a Windows native program to accomplish this, but I really want a pure Java solution. Thank you in advance!

Since Java 7 you can do this easily using the NIO package.
Path target = Paths.get("target");
Path link = Paths.get("link");
Files.createDirectory(target);
Files.createSymbolicLink(link, target);
Do remember that you do need the correct privileges for this. In my unit test I had to run eclipse as an administrator to make it work (same as that I couldn't create a link from a normal cmd.exe)

As far as I know window does not have real symbolic links like Unix-like system do.
However Windows has the following relevant tools:
You can map network drive, i.e. attach drive letter to specified network path. You can definitely do this using WMI. To access WMI from java take a look on tools like JaWin, Jinterop, Jintegra or write WMI script in JScript o VBScript and execute is from Java.
You can use command subst that assigns letter to local file system path. This is the closest approach to Unix soft link.
You can create desktop shortcut. Create one manually and take a look on it. Shortcut is actually regular text file (as far as I remember in INI format). You can easily create one using any language you want including java. This is not soft link but it is clickable.

Analyse SWF-Files with Java

I stumbled upon the need to find out (inside Java code) which files are dynamically loaded by an SWF-file. Is there any possibility to get a list of paths of every object referenced inside?
I tried out some libraries without proper documentation and gave up. Although I ran out of Google Search Phrases... ;)
Maybe there is an external tool which can be accessed by Java via command line?
Ggreat thanks in advance

Maybe you can get to the information you need using the dump tool which is part of Apparat.
I use actionscript more than Java, so I also recommend having a look at AS3SWF which is a great library you could use to load and analyze the swf you need. Think of it as decompiling at runtime.
Either way, the SWF Format Specifications will come in handy.
I'm not sure there's something that does exactly what you want, but I imagine you could collect all the strings (DefineText tags), loop through them and run an URL RegEx against them.

I think even if you could analyze a SWF file, you can't be sure to get this information. I have Flex Project (finally a swf file) which dynamically loads some modules, but the names (URLs) of the available modules are requested from the server. So there is no chance to retrieve this information from the main swf file.

Set write permissions on ProgramData subfolder using JNA

I have a program, written in Java, which originally used its directory in Program Files to write files accessible to all users of this program. This required our users to run as administrator all the time. In an effort to alleviate that, we decided to move files which needed to be written during regular usage to the ProgramData folder using the %ALLUSERSPROFILE% environment variable. Using a subfolder in this directory for our application works great if it is designated as writable during the installation process, which works fine using NSIS.
The problem comes with upgrading existing users. The Java File API provides setWritable but this does not appear to work after testing on development machines. It looks as though the new file API with Java 7 would solve this problem, but with no release date on the horizon I would rather not wait.
It seems the simplest solution would be to use JNA to call the appropriate Windows API call to set this directory writable. Since upgrading the software necessitates admin rights, similar to installing, it should let this change go through fine. However, I'm unsure where to start, having never used JNA before or the Windows API. Suggestions as to which Windows library to load and what functions to call would be appreciated, especially if someone has encountered a similar problem before.

Well, I'm glad you gave some background...You could use JNA, but the easier way would be to execute a call to the command-line utility cacls. It's included by default in Windows XP installations, I believe, so it should do the trick for you. Try Runtime.getRuntime().exec("C:\\Windows\\System32\\cacls.exe"+options)
Check out the documentation here -> http://technet.microsoft.com/en-us/library/bb490872.aspx

I use the follow line:
Runtime.getRuntime().exec( "C:\\Windows\\System32\\icacls.exe \"%ProgramData%\my application" /grant *S-1-5-32-545:(OI)(CI)(W,M)" );
S-1-5-32-545 is the SID for BUILTIN\Users because the name work only on English systems. https://support.microsoft.com/de-de/kb/163846
This give the BUILTIN\Users write access to all files in the given directory independent which user has create it.

Load jar file locally

Let's say I have a jar file and I want users to load it locally from the Internet... to speed up the loading I say... how would I go about doing that?
Like when you access it from http://mydomain.com... the jar file is from my documents/game/test.jar

Look up the URLClassLoader class, I think it will do what you want.
Here is a good description:
http://java.sun.com/developer/technicalArticles/Networking/classloaders/
EDIT: Forget it, Unsigned Applets cannot create ClassLoaders.
For an Applet you will need to download everything at once.

It is exactly the purpose of JNLP files (also called "Java Web Start"). Or I have misunderstood your problem...
You can find the official documentation on Oracle website : http://download.oracle.com/javase/1.5.0/docs/guide/javaws/developersguide/syntax.html
An example famous application using this system : SweetHome3D

I'm not sure if I understand your question, but it sounds like you want Java Web Start.
http://download.oracle.com/javase/tutorial/deployment/webstart/index.html
You would create a jnlp file, and put a link to it on your website. Java will take care of downloading the file and starting it. The .jar file would be stored in a cache, and it shouldn't need to be redownloaded unless the cache is cleared or you replace your old .jar file with a new one.

Will this work on Unix?

This Java code lists files in a directory on a Windows shared drive. Will it work correctly on a Unix system?
File directory = new File("\\\\server/Shared/stuff/mystuff");
for (File file: directory.listFiles()) {
System.out.println(file);
}

Short answer: No.
Long answer: Do you have samba installed? Even then you need to mount the the share. So it probably won't work.
EDIT
Java delegates the call to the underlying OS eventually. Since Unix doesn't know what the \\SERVERNAME path means, Java doesn't know what it means either. What you have to do, to get this to work is mount the drive explicitly using Samba. Your other option, if you are running Ubuntu, is look under .gvfs in your home directory. Ubuntu creates a mount there for your Samba shares, which you should be able to access using Java. If you don't want to rely on external tools, try JCIFS for a pure-Java solution.

No...
Just let the user select the right path and use an OS dependent file-selection dialog.

On my system (Debian Sid with Gnome 2.30 Desktop) I have to select "smb:///server/Shared/..." to achieve the same behaviour. I think, that GVFS (Gnome Virtual File System) using smbfs drivers handles the real connection in the background...

No, as that is a UNC Path, which is a windowsism.
Are you trying to access a windows share from unix? Then have a look at jcifs.

The counter question I get when seeing this is: "Why would you want to hard-code a path in your application?"
Even if it was just for the example and you intend to load the path from a property file or anything, I still think you are on the wrong track here.
First of all you will want to avoid absolute paths like the plague. Relative paths are sort of ok. You can use slash ('/') characters in paths hardcoded, it will work on both Windows and Linux/Mac. Basically all platforms.
Second of all, why use paths at all? This is the internet age. Use URL's! file: URL's will accomplish the same thing as file paths, but using URL's make your app accept resources from other sources such as web sites and FTP as well.
Third of all, avoid the File class. If you invent a good way to do that, you are out of the woodworks completely. Use URL's together with getResource and getResourceAsStream and your app will work platform independent and across network boundaries over the internet.